A broadband optical communication system, particularly for the subscriber area, comprising at least one optical transmitter, at least one optical receiver, and an optical waveguide in which only the fundamental mode can propagate above a cutoff wavelength, e.g., 1,280 nm, is described in "ntz," Vol. 39 (1986), No. 7, pp. 484-489. In that prior art printed publication, it is taught that a single-mode optical waveguide which has the smallest loss and the largest bandwidth in the optical long-wave range from 1300 nm to 1600 nm is a suitable transmission medium which is suitable for all broadband optical communication systems, including the subscriber area where the subscribers are connected to the local exchange in a star network.
As is well known, such "single-mode" optical waveguides are in fact single-mode only for wavelengths above a certain cutoff wavelength (which depends on the core diameter and the refractive indices of the core and the cladding). Above such a cutoff wavelength, only the fundamental mode can propagate; at wavelengths below this cutoff wavelength, two or more modes can propagate (see "ntz," Vol. 39, [1986], pp. 454-459.)
In the first-mentioned publication, it is stated that the optical transmitters and receivers must be tuned to the long-wave optical range (1300 nm to 1600 nm), and that great efforts still need to be made to achieve low-cost manufacture. It is to be noted that no low-cost solution to the problem of transmitting optical signals over optical waveguides in the subscriber area is given in the cited printed publication.
"ntz," Vol. 39 (1986), No. 7, pp, 502-508, contains additional teachings to the effect that a single-mode optical waveguide is the type of optical-waveguide best suited for the optical subscriber line, but that the high costs of the necessary optical-to-electric transducers prevent an early introduction of broadband optical subscriber lines.